The Neostratotype of Itapecuru Formation (Lower-Middle Albian) and Its Impact for Mesozoic Stratigraphy of Parnaíba Basin

Abstract

This study defines the neostratotype of the Lower-Middle Albian Itapecuru Formation in the Parnaíba Basin, Northeast Brazil. In this sedimentary succession along the right bank of the Itapecuru river near the Itapecuru-Mirim City, Maranhão State, three lithofacies associations are recognized. the first is silty claystone with some very fine sand, micaceous, reddish color, thin laminated, showing a tabular aspect, interpreted as floodplain fines in a distal position. The second is clayey siltstone, reddish color, with ripple cross-lamination, very thin cross-laminated wacke lenses, grading to thin parallel lamination, in apparently tabular layers, interpreted as crevasse splay and distributive channels deposits in successive avulsion events. The third is fine quartz wacke, reddish to grayish color, showing grouped trough cross bedding, interpreted as channel filling deposits. These facies associations correspond to part of a fluvial depositional system, with predominantly fine-grained rocks, and small lakes in the floodplain, in an oxidizing environment and marked by seasonality. These field data, reinforced by grain size and petrographic analyses showed that, contrary to previous descriptions, the Itapecuru Formation consists mainly of mudrocks. this research also shows that the medium to coarse sandstones and conglomerates, previously included in the Itapecuru Formation, belong to the underlying Grajaú Formation.

Distribution of physical and chemical variables in the water column and characterization of the bottom sediment in a macrotidal estuary on the Amazon coast of the state of Maranhão, Brazil

“…Stratigraphically, the basin has sequences of the Itapecuru Formation (formed during the Cretaceous), subdivided into the Psammitic Lower Member and Alcântara Upper Member, composed generally of sandstone, mudstone, shale, and limestone. The sediment is composed of clay, silt, very fine sand, and limestone (Corrêa-Martins, 2019).…”

Tectonic aspects of the Rio Parnaíba Lineament, Duque Bacelar Region, Maranhão State, based on the record of Dinosauria, Spinosaurinae

“…Dinosaur teeth, mainly theropods, are commonly collected in the Cretaceous strata of the Itapecuru Formation (which crops out extensively in the central, northern, and northeastern regions of Maranhão) and Alcântara Formation, with fossiliferous outcrops concentrated in the northern part of the state (Corrêa Martins, 1997;Carvalho et al, 2003;Medeiros & Schultz, 2001Lindoso et al, 2012;Medeiros et al, 2014Medeiros et al, , 2019Lindoso et al, 2012;Sousa et al, 2015;Letizio et al, 2022). Records of the Itapecuru Formation occur near Duque Bacelar, immediately west of the Parnaíba River Valley (CPRM, 2012); however, no fossiliferous occurrences have been reported.…”